The present invention relates generally to a piston, and more particularly to a piston of an accumulator assembly for receiving and temporarily storing fluid.
Braking a vehicle in a controlled manner under adverse conditions such as rain, snow, or ice generally requires precise application of the brakes by the vehicle driver. Under these conditions, or in panic stop situations, a driver will often apply excessive brake pressure, thus causing the wheels to lock such that excessive slippage between the wheels and the road surface takes place. Wheel lockup conditions can lead to loss of directional stability and, possibly, uncontrolled vehicle spinout.
Generally, prior art anti-lock brake systems include a central control unit for monitoring the speed of the controlled wheels to determine the deceleration of the controlled wheels. When the brakes of the vehicle are applied and the wheel deceleration of the monitored wheels exceeds a predetermined deceleration threshold, indicating that there is wheel slippage and the wheels are approaching a lockup condition, the central control unit functions to control the application of hydraulic pressure through a control valve means to the associated brakes to prevent lockup of the controlled wheels. Typically, the anti-lock brake system includes means for cyclically reducing and reapplying pressure to the associated brakes to limit wheel slippage to a safe level while continuing to produce adequate brake torque to decelerate the vehicle as desired by the driver.
In controlling the application of pressure to selected wheel brakes, many systems utilize a low pressure accumulator which is operative to temporarily receive and store brake fluid during pressure reduction phases of the anti-lock operation.
The invention relates to a piston, especially a piston of a low pressure fluid accumulator of a hydraulic control unit of a vehicle brake system. The piston includes a cylindrical body having an outer surface defining a first end surface of the piston. The first end surface includes a plurality of interconnected ridges. The ridges have outer surfaces and form cavities therebetween. Each ridge is adapted to provide a sealing surface between the first end surface of the piston and an inner surface of a fluid accumulator in which the piston may be inserted.
In another embodiment of the invention the closed end of the piston includes a thick self-supporting wall. A thin skirt extends from the thick self-supporting wall toward the open end of the piston. A plurality of axially extending skirt support ribs is formed on the inner surface of the piston skirt.
In another embodiment of the invention the piston includes a substantially cup-shaped cylindrical body having an inner surface defining an axial bore. The axial bore extends from an open end of the piston body to a closed end of the piston body. An outer surface of the closed end defines a first end surface of the piston body. An annular boss is formed at a periphery of the first end surface. An annular ridge is formed centrally on the first end surface, and defines a central recess. The first end surface includes a plurality of ridges extending radially from the centrally formed annular ridge to the annular boss. Adjacent ridges define cavities therebetween.